Lewy Bodies (LBs) are distinctive intraneural cytoplasmic inclusions of unknown pathogenesis. They are found in all cases of Parkinson's Disease (PD), and diffuse Lewy body disease (DLBD) (also known as the Lewy body variant of Alzheimer's disease). In addition, LBs are occasionally found in a few other pathological processes. The composition of LBs by direct biochemical methods and their role in these diseases processes remains unknown. Recently we have shown that antibodies raised to purified amyloid extracted from familial amyloidosis, Finnish type (FAF) immunoreact with LBs. This immunoreactivity is specific, as it was absorbed by the purified amyloid proteins and is unaffected by other antigens such as ubiquitin, neurofilament proteins and tubulin which have been shown by immunohistochemical methods to be present in LBs. FAF amyloid has been found to be an aberrant degradation product, starting at position 173, of gelsolin, an actin modulating protein. The amino acid sequence shows heterogeneity at the N-terminus and at position 15, where asparagine substitutes for aspartic acid. At the DNA level, a guanine to adenine transition corresponding to nucleotide 654 of the human gelsolin has been found in all FAF patients tested so far. Commercially available anti- gelsolin antibodies raised to the carboxy-terminus of the molecule (away from the amyloidogenic region) do not immunostain LBs. This raises the possibility that LBs also contain an abnormal fragment of gelsolin that is closer to the amino terminal of the molecule. We plan: (1) To perform an immunohistochemical survey of DLBD, Alzheimer's disease, and Parkinson's disease cases with the anti-FAF antibody, as well as with antibodies to intact gelsolin, fragments and synthetic peptides of different regions of the gelsolin molecule, to evaluate patterns of immunoreactivity and epitope mapping; (2) To characterize the composition of the purified LBs preparation by using Western blotting and direct amino acid sequencing to sequence gelsolin and/or its fragments; (3) To investigate the biological activity of gelsolin isolated from DLBD, PD, AD, and control CSF to see if there are any abnormalities; (4) To clone the gelsolin gene from familial PD patients and screen for any variations; (5) To investigate cerebral spinal fluid from patients with PD, DLBD, other neurodegenerative disorder, controls and AD for the presence of any abnormal gelsolin fragments that could be used as a diagnostic test. Together these studies will expand knowledge about LBs and the role gelsolin plays in their formation.